WASHINGTON - The government is imposing fines for the first time against airlines for stranding passengers on an airport tarmac, the Department of Transportation said Tuesday.

The department said it has levied a precedent-setting $175,000 in fines against three airlines for their role in the stranding of passengers overnight in a plane at Rochester, Minn., on Aug. 8.

Continental Express Flight 2816 was en route from Houston to Minneapolis carrying 47 passengers when thunderstorms forced it to divert to Rochester, where it landed about 12:30 a.m. The airport was closed, and Mesaba Airlines employees - the only airline employees at the airport at the time - refused to open the terminal for the stranded passengers.

Continental Airlines, and its regional airline partner ExpressJet Airlines, which operated the flight for Continental, were each fined $50,000. ExpressJet spokeswoman Kristy Nicholas said the airline can avoid paying half the fines if it spends the same amount of money on additional training for their employees on how to handle extended tarmac delays.

The department imposed the largest penalty - $75,000 - on Mesaba Airlines, a subsidiary of Northwest Airlines, which was acquired by Delta Air Lines last year.

"I hope that this sends a signal to the rest of the airline industry that we expect airlines to respect the rights of air travelers," Transportation Secretary Ray LaHood said. "We will also use what we have learned from this investigation to strengthen protections for airline passengers subjected to long tarmac delays."

The passengers of Flight 2816 were kept waiting nearly six hours inside the cramped regional airliner amid wailing babies and a smelly toilet even though they were only 50 yards from a terminal. The captain of the flight repeatedly pleaded to allow the passengers to deplane and enter the terminal.

In the morning they were allowed to disembark. They spent about 2 1/2 hours inside the terminal before reboarding the same plane to complete their trip to Minneapolis.

Passenger Link Christin praised the department's action.

"A conclusion that there was some wrongdoing or negligence is more important to me than the amount of the fine," said Christin, a lecturer at William Mitchell College of Law in St. Paul, Minn.

The department's actions come as Congress weighs passengers' rights legislation that would place a three-hour cap on how long airlines can keep passengers waiting on tarmacs before they have to offer them the opportunity to deplane or return to a gate. The measure would give a flight's captain the authority to extend the wait an additional half hour if it appears that clearance to take off is near.